The iambic trimeter derives its name from its essential shape, which is three metrical units (hence trimeter) which are each basically iambic in form. The iambic metron has the following shape (where the x is an anceps, the - is a longum, and the u is a brevis):
Hence, reversing the current running though a wire will have the affect of reversing the direction of the magnetic force at a point some distance away from the wire. The affect that this has on the overall magnetic field depends on the shape of the wire.
Even the magnetic field produced by a current-carrying wire must form complete loops. Above, you were told that a loop of current-carrying wire produces a magnetic field along the axis of the wire. The right-hand rule gives the direction of the field inside the loop of wire. The magnetic field turns back the other way outside of the loop. As shown in the figure on the right, this magnetic field from a loop of current-carrying wire looks similar to the field from a permanent bar magnet.